US3922381A - Chemically treated carrier particles for use in electrophotographic process - Google Patents

Abstract

Carrier particles for use in an electrophotographic process are prepared by applying a perfluoro acid to the surface of the carrier particle. The resulting carriers are long lived and capable of imparting a positive triboelectric charge to electroscopic powders mixed therewith.

Description

{baited States Patent 1 Datta 51 Nov. 25, 1975 CHEMICALLY TREATED CARRIER PARTICLES FOR USE IN ELECTROPHOTOGRAPHIC PROCESS [75] Inventor: Pabitra Datta, Lyndhurst, Ohio [73] Assignee: Addressorgrap Multigraph Corporation, Cleveland, Ohio [22] Filed: June 14, 1974 [21] Appl. No.: 479,298

[52] U.S. Cl. 427/21; 96/15 D; 252/621 P; 427/18; 427/19; 427/20; 427/215; 427/216; 427/220; 428/403; 428/404; 428/406 [51] Int. Cl. ..G03G 13/08; G03G 13/09; BO5D 5/12;C03C 17/28 [58] Field of Search 117/100 R, 100 M, 17.5;

OPT/64L DEA/5777 3,627,682 12/1971 Hall et a1 252/621 P X 3,632,512 l/1972 Miller 252/621 P 3,652,315 3/1972 Matsuo et a1. 117/17.5 3,676,350 7/1972 Wright et a1. 252/621 P 3,718,594 2/1973 Miller 117/100 M X 3,761,413 9/1973 Hulse 252/621 3,778,262 12/1973 Queener et a1. 117/17.5 X 3,796,664 3/1974 Hayashi et a1. 252/621 3,798,167 3/1974 Kukla et a1. 252/621 P 3,811,880 5/1974 Browning 252/621 X FOREIGN PATENTS OR APPLICATIONS 42-19755 10/1967 Japan 252/621 P Primary Examiner-Charles L.'Bowers, Jr. Assistant ExaminerJohn R. Miller Attorney, Agent, or FirmMichael A. Kondzella [57] ABSTRACT Carrier particles for use in an electrophotographic process are prepared by applying a perfluoro acid to the surface of the carrier particle. The resulting carriers are long lived and capable of imparting a positive triboelectric charge to electroscopic powders mixed therewith.

18 Claims, 2 Drawing Figures AMA/5E7? a: ca /afiwasm/os) CI-IEMICALLY TREATED CARRIER PARTICLES FOR USE IN ELECTROPIIOTOGRAPHIC PROCESS BACKGROUND OF THE INVENTION This invention relates to carriers for use in developer formulations which charge electroscopic powders triboelectrically. These carriers are useful in electrophotographic processes for developing latent electrostatic images in which a colored toner carried by the carrier particle is caused to be attracted from the carrier particle to develop the latent electrostatic image.

In the electrophotographic process it is necessary to use a carrier for the toner in order to produce an elec trostatic charge upon the toner particles. Various kinds of developing processes are known including cascade, powder cloud and magnetic brush processes. In each of these processes it is necessary that the carrier used have certain triboelectric properties so that it is capable of imparting to the toner particles an electrostatic charge of the proper polarity and magnitude. Where uncoated carrier particles are used it has been necessary to select a toner having the desired triboelectric properties. Recently, it has been found that the carrier particles can be coated with various types of polymeric coatings to permit variation in the triboelectric properties thereof. One such method is disclosed in US. Pat. No. 3,811,880 to Luther C. Browning, assigned to the same assignee as this invention.

Although polymeric coatings of this type enable a certain degree of control of the triboelectric properties of the developer mix, it has been found that in use in the environment of electrophotographic reproduction machines such carrier particles are subject to aging which limits their effectiveness. Wearing away and removal of part of the polymeric coating upon the surface of the carrier particles is another problem encountered. This may result in undesired abrasion of the photoconductive surface used for imaging and also cause bias shorting.

Another problem inherent in the use of polymeric coatings for carrier particles is the phenomenon known as bound toner. Through a mechanism which is not clearly understood prolonged usage of developer mixes including polymeric coated carrier particles results in toner being adhered onto the surface of the coated carrier causing a decrease in the effectiveness of the toning process and hence in the overall development of the images being reproduced.

08.] EC TS It is accordingly an object of this invention to provide carriers for toners which are not subject to the disadvantages mentioned above.

Another object of this invention is to provide carrier particles which have an enhanced longevity.

Another object of this invention is to provide carrier particles which are capable of imparting desired triboelectric properties to various types of toners.

Other objects and advantages of this invention will become apparent in the following detailed disclosure and description.

SUMMARY OF THE INVENTION Chemically treated carrier particles can be used in developer mixes in order to increase the useful life of the developer and also to provide desired triboelectric properties. A chemical treatment for the purpose of adhering a perfluoro carboxylic acid to the surface of a carrier matrix has been found to result in carriers having a longevity which is significantly greater than untreated carrier particles or carrier particles coated with various kinds of polymers. A more efficient carrier with respect to triboelectric properties, a carrier having low surface energy and a low coefficient of friction and a carrier which does not need to be replenished as frequently as other types of carriers is thereby provided.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a series of curves showing variation in image density as a function of the number of copies produced for various types of carriers.

FIG. 2 is a series of curves showing bound toner as a function of the number of copies produced for various types of carriers.

DETAILED DESCRIPTION OF THE INVENTION It has been found that the various problems encountered with previously available carriers are generally obviated by the use of a carrier particle to the surface of which is adhered a perfluoro carboxylic acid or derivative thereof. The perfluoro acids contemplated by this invention are those perfluorinated and substantially perfluorinated carboxylic acids, both aliphatic and aromatic, which have carbon chains of from 3 to 18 carbon atoms in length. Exemplary of such acids are perfluoropropionic acid, perfluorobutyric acid, perfluorovaleric acid, perfluoroadipic acid, perfluoroheptanoic acid, perfluorooctanoic acid, perfluorononanoic acid, perfluorodecanoic acid, 11 H eicosafluoroundecanoic acid, as well as the higher molecular weight aliphatic acids and aromatic acids such as perfluorobenzoic acid. Polycarboxylic acids can also be used, for example, perfluorosuccinic acid or perfluoroglutaric acid. Derivatives of perfluoro carboxylic acids such as esters and amides can also be used.

As carrier matrix materials it is possible to use a wide variety of substances, for example glass beads, ceramic beads, grains of sand or metallic particles. Non-metallic matrix materials are useful where a cascade development system is utilized although metallic matrices can also be used in cascade development. Where a magnetic brush developing system is used it is necessary that the matrix be magnetic. For this purpose various irons and steels have been used, for example, spherical steel beads and irregularly shaped iron powders.

The desired chemical treatment can be accomplished in a number of ways. In general, it is merely necessary to mix the carrier matrix material with a solution of the perfluoro carboxylic acid. Ordinarily, adherence of the perfluoro acid to the powder or bead occurs in a dilute solution of the perfluoro acid in a suitable solvent such as an alcohol, ketone or hydrocarbon at room temperature in a matter of hours. It is desirable that the matrix material being used be thoroughly cleaned and dried prior to treatment with the perfluoro acid and that the product resulting from treatment of the matrix material with the perfluoro acid solution be thoroughly dried before use.

The matrix particles treated with a perfluoro acid according to this invention are believed to constitute a monomolecular film of the acid adhered to the surface of the matrix particle, although thicker films may be produced if desired. Adherence of the perfluoro acid to the carrier matrix is believed to be by chemical adsorption.

The resulting carriers are found to have a longer useful life than prior art carriers in the environmentof electrophotographic development. Because these carriers have a low surface energy, reduced toner filming, characterized as bound toner" is realized. In addition the adherence of the film of perfluoro carboxylic acid to the carrier matrix material reduces flaking, chipping and spalling of the carrier.

Further, as pointed out above, the triboelectric properties of the carriers of this invention are such that most toners will be charged with a positive polarity when used with these carriers. Even polytetrafluoroethylene (Teflon) and polyethylene can be charged positively using the carriers of this invention. Since most commercially available toners are less electronegative than Teflon or polyethylene they are charged with a positive polarity almost without exception.

With the outstanding triboelectric properties of the carriers of this invention and the physical properties mentioned above, namely the low surface energy, the low coefficient of friction and the pronounced adherence of the perfluoro carboxylic acid to the carrier matrix material these carriers represent a significant improvement over carriers which have been previously used. In addition to the long life of the carriers themselves the particular combination of properties increases the life of the photoconductor used in the electrophotographic process and also results in very high quality copies being produced.

The durability and effectiveness of these carriers is greatly enhanced because of the extremely thin film of perfluoro carboxylic acid upon the surface of the carrier matrix material.

Another advantage of the carriers of this inventionis that the toner filming or bound toner determined using various commercially available toners with these carriers is considerably less than in the case of carrier particles which have been coated with low surface energy polymerssuch as polyvinylidene fluoride or silicones, which show little if any improvement over uncoated carrier matrix material. The low percentage of bound toner" indicates that the carriers ofthis invention can be used much more successfully than previously available carriers since their efficiency is not reduced by toner filming upon the carrier particles to the same extent as prior art carriers.

This invention will be better understood by reference to the following examples which are intended to illustrate but not to unnecessarily limit the scope of this invention which is defined in the claims appended hereto.

EXAMPLE 1 A 4 kilogram quantity of 150;; average particle size spherical steel beads was cleaned with trichloroethane in an ultrasonic cleaner and then dried in a fluidized oven at 80C. The cleaned and dried steel beads were then poured into a solution of 4 g. of perfluorooctanoic acid (PFOA) in 800 g. of methanol and stirred for 2 hours. The alcoholic solution was then decanted and the steel beads were washed with an equivalent amount of methanol and dried in a fluidized bed oven at 60C for 1 hour.

EXAMPLE 2 A quantity of 4 kilograms of 150,1; average particle size spherical steel beads was cleaned with trichloro- The cleaned and dried steel beads were mixed with a toner containing polymers prepared from styrene and acrylic monomers. polyvinyl butyral and carbon black in a weight ratio of 40:1. Zinc oxide coated paper was charged negatively by means of a corona discharge using a potential of 5000 volts, exposed through a photographic transparency and toned with a hand-held magnetic brtish using this developer. Reversal copies were produced.

Triboelectric properties of this toner were determined in the following manner:

A sheet of toner about 1 mm. thick was formed upon a steel plate by melting the toner onto the metal. The resulting toner sheet was then gently rubbed in the carrier and the carrier was removed by shaking or lightly C K E,,A/I in parallel with a resistance R pr/A with a voltage across the plates of:

where 6,, is the permitivity of free space.

The surface charge density o' associated with the toner-carrier triboelectric interaction was thus easily calculated from the measured voltage drop across the toner sheet, the dielectric constant and the thickness of the sheet.

The sheet thickness was determined by measuring the thickness of the sheet plus metal plate with calipers and substracting the measured thickness of the bare metal plate. The sheet dielectric constant was determined in the standard manner by l) measuring the capacitance of the sheet placed between electrodes of known area and, (2) dividing that value by the calculated unloaded capacitance of the electrodes separated by a space equal to the sheet thickness.

Toner sheets made by carefully melting the toner powder onto the plate were often found to have edges slightly lower than the centers. In order to avoid any inethane in an ultrasonic cleaner and then dried in a fluidized oven at C.

accuracies occasioned by the method of sheet preparation care was taken to measure the voltage only in the regions where the thickness was uniform and easy to measure.

Using the above-described technique this toner was found to have a surface charge density 0" of 0.l8 X 10" coulomb per square centimeter when charged with steel beads.

EXAMPLE 3 using a potential of 5000 volts, exposed through a photographic transparency and toned with a hand-held magnetic brush using this developer. The surface charge density was found to be +1.8 X coulomb per square centimeter. Positive copies were produced.

EXAMPLE 4 A 1500 g. quantity of PFOA treated steel beads prepared according to Example 1 were mixed with 22.5 g. of the toner of Example 2. The resulting developer was poured into the toning unit of an Addressograph-Multigraph Model 2000 electrostatic copying machine. Copies of a photographic transparency were made using zinc oxide coated paper. The optical density of the copies produced was determined by means of a MAC- BETH RD5 19 densitometer.

A curve showing optical density as a function of the number of copies produced was plotted and is shown as Curve A in FIG. 1. Using this developer 180,000 copies were produced before any'adverse effect upon copy quality was observed.

Fresh developer was added and the machine was run continuously for 240 hours. One hour of running time is equivalent to the production of 1200 copies. Every 12 to 24 hours a small amount of developer was removed from the toning unit and examined microscopically for toner filming.

No toner adhered to the surface of the carrier beads (bound toner) was observed prior to 192 hours running time. Percentage of bound toner was determined using the analytical technique described in Denshi Shashin (Electrophotography) .10, 14 (1971 The analytical results were plotted and are shown in Curve F of FIG. 2 which shows the percentage of bound toner determined as a function of the number of copies produced.

EXAMPLE 5 A developer consisting of 1500 g. of cleaned and dried 150p. average particle size steel beads and 22.5 g. of a toner containing polyamide resin, maleic modified rosin, polyketone resin, polyethylene, lithium stearate, carbon black and a positive orienting dye was tested according to the procedure of Example 4.

Curve B of FIG. 1 shows the optical densities observed and Curve G of FIG. 2 shows the bound toner determinations. The surface charge density was found to be +1.0 X 10 coulomb per square centimeter. About 12,000 copies could be produced before the copy density became unsatisfactory.

EXAMPLE 6 The toner of Example 5 was mixed with PFOA treated steel beads prepared according to the procedure of Example 1 and copies were produced according to the procedure of Example 4.

The results are shown in Curve C of FIG. 1. The surface charge density was found to be +6.2 X 10' coulomb per square centimeter. Copy quality was maintained for 240,000 copies.

EXAMPLE 7 A developer consisting of 50 g. of cleaned and dried 150 average particle size steel beads and 0.75 g. of a toner containing copolymers of styrene and butyl methacrylate, carbon black and a negative orienting dye was tested according to the procedure of Example 2.

6 The surface charge density was found to be -1.0 X 10* coulomb per square centimeter. Reversal copies were produced.

EXAMPLE 8 The toner of Example 7 was mixed with PFOA treated steel beads prepared according to the procedure of Example 1 and tested according to the procedure of Example 2.

The surface charge density was found to be +4.9 X 10 coulomb per square centimeter. Positive copies were produced.

EXAMPLE 9 A developer consisting of 50g. of cleaned and dried 150paverage particle size steel beads and 0.75 g. of a toner containing copolymers of styrene and n-butyl methacrylate, maleic modified rosin, polyvinyl stearate and carbon black was tested according to the procedure of Example 2.

The surface charge density was found to be -0.4 X 10' coulomb per square centimeter. Reversal copies were produced.

EXAMPLE 10 EXAMPLE 1 1 The procedure of Example 1 was followed except that iron powder having a particle size range of ,u. to 200p. was used.

EXAMPLE 12 The procedure of Example 2 was followed except that the iron powder of Example 11 was used.

The surface charge density was found to be 0.5 X 10 coulomb per square centimeter and reversal copies were produced. Similar results were obtained with the toners of Examples 7 and 9.

EXAMPLE 13 The procedure of Example 2 was followed except that the carrier used was the PFOA treated iron powder of Example 11.

The surface charge density was found to be +1.8 X 10 coulomb per square centimeter. Positive images were produced. Similar results were observed with the toners of Examples 7 and 9.

. EXAMPLE 14 The procedure of Example 4 was followed except that the developer consisted of the iron powder of Example 11 and 22.5 g. of the toner of Example 5.

The surface charge density was found to be +1.15 X .10 coulomb per square centimeter. Copy quality began to fall off after about 15,000 copies. The optical densities are shown in Curve D of FIG. L'Microscopic examination revealed toner filming.

EXAMPLE 15 The procedure of Example 4 was followed using the carrier of Example ll and the toner of Example 5.

The optical densities are shown in Curve E of FIG. 1. Copy quality was maintained for 240,000 copies. The surface charge density was found to be +1.4 X 10 coulomb per square centimeter.

Other iron carrier matrix materials were used with similar effect. Various sizes of irregular shaped iron particles from about 50;; to 200p. were found to be effective as were spherical iron beads from about 150; to 500;.t.

In addition to PFOA other perfluorinated and substantially perfluorinated acids and derivatives thereof were found to impart a positive charge to various toners. Exemplary of such other perfluoro acids are perfluoropropionic acid, perfluorobutyric acid, perfluorodecanoic acid and perfluoroglutaric acid. An example of a substantially perfluorinated acid is 11- H eicosafluoroundecanoic acid. An example of an acid derivative which can be used in this invention is perfluoroacetamide.

The carriers of this invention generally were effective to impart a positive charge to toners of widely varying types. In addition these carriers charged sheets of polyethylene, polytetrafluoroethylene (Teflon) and polymethacrylates positively.

EXAMPLE 16 A 300 g. quantity of BONDERITE 860 (Parker Rust Proof Division, Hooker Chemical Corporation, Detroit, Mich), a phosphating agent for producing a corrosion-inhibiting finish on metals, was mixed with 4800 g. of cold water and the mixture heated on a hot plate to 80 C. and then poured into a 2 gallon stainless steel container of a pony mixer and stirred for 1 minute.

Spherical steel beads of 150;; average particle size in a quantity of kilograms were added and mixed for minutes, then decanted and washed with cold water until the solution was clear and dried in a fluidized oven at 100 C. for 2 hours.

The resistivity of the resulting phosphated steel beads was found to be about 1 X 10 to l X 10 ohms compared to a resistivity of about 1 X 10 ohms for the untreated beads.

EXAMPLE 17 A quantity of 4 kilograms of the phosphated steel beads prepared according to Example 16 was poured into a solution of 4 g. of PFOA in 800 g. of methanol and stirred for 2 hours. The alcoholic solution was then decanted and the PFOA treated beads were washed with an equivalent amount of methanol and dried in a fluidized bed oven at 60C for 1 hour.

EXAMPLE 18 EXAMPLE l9 The procedure of Example 2 was followed using the PFOA treated phosphated steel beads of Example 17.

Positive copies were produced using the toners of Examples 2, 7 and 9.

EXAMPLE 20 The procedure of Example 4 was followed using the PFOA coated phosphated steel beads of Example 17. Copy quality was maintained for 200,000 copies.

EXAMPLE 21 A 2 kilogram quantity of 650 micron average particle size Ottawa sand was poured into a solution of 5 grams of PFOA in 400 grams of methanol and mixed for 2 hours. The alcoholic solution was then decanted and the sand particles washed with an equivalent amount of methanol and dried in a fluidized bed oven at 60C for 1 hour.

EXAMPLE 22 Ottawa sand (650 micron particle size) in a quantity of 50 grams was mixed in a plastic bag with 0.5 gram of the toner of Example 2.

The toner was found to have a surface charge density of 0.3 X 10" coulomb per square centimeter. Zinc oxide coated paper was charged negatively by means of a corona discharge using a potential of 5,000 volts, ex posed through a photographic transparency and toned by cascading the above described developer mixture across the surface of the exposed zinc oxide paper. Reversal copies were produced.

EXAMPLE 23 The carrier particles of Example 21 were mixed with the toner of Example 2 and tested according to the procedure of Example 22.

The surface charge density was found to be +2.0 X 10" coulomb per square centimeter. Positive copies were produced.

EXAMPLE 24 The procedure of Example 22 was followed except that the toner of Example 5 was used.

The surface charge density was found to be +2.7 X 10" coulomb per square centimeter. Copies of relatively low optical density were produced.

EXAMPLE 25 The procedure of Example 23 was followed using the toner of Example 5.

The surface charge density was found to be +ll X 10 coulomb per square centimeter. Positive copies of good optical density were produced.

EXAMPLE 26 The procedure of Example 22 was followed using the toner of Example 9.

The surface charge density was found to be +0.53 X 10 coulomb per square centimeter. Copies having a significant amount of background and some reversal characteristics were produced.

EXAMPLE 27 The procedure of Example 23 was followed except that the toner of Example 9 was used.

The surface charge density was found to be +2.0 l0- coulomb per square centimeter. Positive copies of good optical density were produced.

lt can thus be seen that the carriers of this invention can be used to produce good positive copies using a variety of toners and by any desired development method; such as magnetic brush development or cas- 9 cade development. Particularly noteworthy is the apparent ability of the carriers of this invention to impart a positive charge to most types of toners.

This invention has been described with respect to a limited number of specific embodiments. However, it is intended that alternative compositions and methods can be used and it is to be understood that this invention is not to be limited except in accordance with the claims appended hereto.

I claim:

1. A carrier for use in electrophotographic development of latent electrostatic images capable of inducing an electrostatic charge in a toner mixed therewith which comprises a member selected from the group consisting of metallic particles and siliceous particles to the surface of which is adhered a member selected from the group consisting of perfluorinated and substantially perfluorinated carboxylic acids containing from 3 to 18 carbon atoms and esters and amides thereof.

2. A composition according to claim 1 wherein the carrier comprises a monomolecular layer of said acid, ester or amide adhered to the surface of said particles by chemical adsorption.

3. A composition according to claim 1 wherein said acid is perfluorooctanoic acid.

4. A composition according to claim 1 wherein said acid is perfluoropropionic acid.

5. A composition according to claim 1 wherein said acid is perfluorobutyric acid.

6. A composition according to claim 1 wherein said acid is perfluorodecanoic acid.

7. A composition according to claim 1 wherein said acid is 11 l-l eicosafluoroundecanoic acid.

8. A composition according to claim 1 wherein said acid is perfluoroglutaric acid.

9. A composition according to claim 1 wherein said amide is perfluoroacetamide.

10. A composition according to claim 1 wherein said electrostatic charge is of a positive polarity.

11. A composition according to claim 1 wherein said particles are magnetic.

12. A composition according to claim 1 wherein said particles are non-magnetic.

13. A composition according to claim 1 wherein said particles are iron.

14. A composition according to claim 1 wherein said particles are spherical iron beads.

15. A composition according to claim 1 wherein said particles are phosphated iron.

16. A process for developing a latent electrostatic image which comprises 7 mixing an electroscopic powder with a carrier comprising a member selected from the group consisting of metallic particles and siliceous particles to the surface of which is adhered a member selected from the group consisting of perfluorinated and substantially perfluorinated carboxylic acids containing from 3 to 18 carbon atoms and esters and amides thereof to impart opposite electrostatic charges to said electroscopic powder and said carrier, whereby said electroscopic powder is attracted to said carrier and transferring said electroscopic powder from said carrier to said latent electrostatic image.

17. A process according to claim 16 wherein-said transferring step is accomplished by means of cascade development.

18. A process according to claim 16 wherein said transferring step is accomplished bymeans of magnetic brush development.

UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTEQN PATENT NO. 3,922,381

DATED 2 November 25, 1975 iNvENToRd) Pabitra Datta it is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Title Page, [73], change "Addressorgrap" to Addressograph Signed and $caled this fourth Day at May 1976 [SEAL] AIIESI.

RUTH C. M X SON C. MARSHALL DANN Arresting Officer (ommissimu'r UfPaILH'S and Trademarks

Claims (18)

1. A CARRIER FOR USE IN ELECTROPHOTOGRAPHIC DEVELOPMENT OF LATENT ELECTROSTATIC IMAGES CAPABLE OF INDUCING AN ELECTROSTATIC CHARGE IN A TONER MIXED THEREWITH WHICH COMPRISES A MEMBER SELECTED FROM THE GROUP CONSISTING OF METALLIC PARTICLES AND SILICEOUS PARTICLES TO THE SURFACE OF WHICH IS ADHERED A MEMBER SELECTED FROM THE GROUP CONSISTING OF PERFLUORINATED AND SUBSTANTIALLY PERFLUORINATED CARBOXYLIC ACIDS CONTAINING FROM 3 TO 18 CARBON ATOMS AND ESTERS AND AMIDES THEREOF.

2. A composition according to claim 1 wherein the carrier comprises a monomolecular layer of Said acid, ester or amide adhered to the surface of said particles by chemical adsorption.

3. A composition according to claim 1 wherein said acid is perfluorooctanoic acid.

4. A composition according to claim 1 wherein said acid is perfluoropropionic acid.

5. A composition according to claim 1 wherein said acid is perfluorobutyric acid.

6. A composition according to claim 1 wherein said acid is perfluorodecanoic acid.

7. A composition according to claim 1 wherein said acid is 11 -H - eicosafluoroundecanoic acid.

8. A composition according to claim 1 wherein said acid is perfluoroglutaric acid.

9. A composition according to claim 1 wherein said amide is perfluoroacetamide.

10. A composition according to claim 1 wherein said electrostatic charge is of a positive polarity.

11. A composition according to claim 1 wherein said particles are magnetic.

12. A composition according to claim 1 wherein said particles are non-magnetic.

13. A composition according to claim 1 wherein said particles are iron.

14. A composition according to claim 1 wherein said particles are spherical iron beads.

15. A composition according to claim 1 wherein said particles are phosphated iron.

16. A process for developing a latent electrostatic image which comprises mixing an electroscopic powder with a carrier comprising a member selected from the group consisting of metallic particles and siliceous particles to the surface of which is adhered a member selected from the group consisting of perfluorinated and substantially perfluorinated carboxylic acids containing from 3 to 18 carbon atoms and esters and amides thereof to impart opposite electrostatic charges to said electroscopic powder and said carrier, whereby said electroscopic powder is attracted to said carrier and transferring said electroscopic powder from said carrier to said latent electrostatic image.

17. A process according to claim 16 wherein said transferring step is accomplished by means of cascade development.

18. A process according to claim 16 wherein said transferring step is accomplished by means of magnetic brush development.

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